This invention relates to millimeter wave circulators and more particularly to a novel and efficient circulator of this type which is useful in the millimeter (mm) wavelength region. Development of mm wavelength technology has been motivated by a desire to increase utilization of spectrum space and to permit miniaturization of components. Recently dielectric waveguides have been developed for military applications which operate at millimeter wavelengths, that is, between 40 and 220 GHz. At mm wavelengths dielectric waveguides are more efficient than conventional hollow metallic guides. A mm wave dielectric guide can have a width and height of 0.050 and 0.070 inches, respectively. The development of such guides involved a search for a material which would exhibit acceptable losses at these high frequencies. One such material is a ceramic composed of magnesium titanate. The effective utilization of these newly-developed waveguides depends on the development of numerous other control components capable of operating in the same frequency range. The present invention is one of these other components.